diff --git a/lib/include/srsran/rlc/rlc_am_nr.h b/lib/include/srsran/rlc/rlc_am_nr.h
index c35cb4690..c69a921f6 100644
--- a/lib/include/srsran/rlc/rlc_am_nr.h
+++ b/lib/include/srsran/rlc/rlc_am_nr.h
@@ -100,12 +100,14 @@ public:
 
   void stop() final;
 
+  bool inside_tx_window(uint32_t sn);
+
 private:
   rlc_am*       parent = nullptr;
   rlc_am_nr_rx* rx     = nullptr;
 
-  uint32_t       mod_nr = 4096;
-  inline int32_t tx_mod_base_nr(uint32_t sn) { return ((int32_t)sn - (int32_t)st.tx_next_ack) % mod_nr; }
+  uint32_t        mod_nr = 4096;
+  inline uint32_t tx_mod_base_nr(uint32_t sn) const;
 
   /****************************************************************************
    * Configurable parameters
diff --git a/lib/src/rlc/rlc_am_nr.cc b/lib/src/rlc/rlc_am_nr.cc
index e7a879a34..7245de22e 100644
--- a/lib/src/rlc/rlc_am_nr.cc
+++ b/lib/src/rlc/rlc_am_nr.cc
@@ -381,6 +381,11 @@ uint8_t rlc_am_nr_tx::get_pdu_poll()
   return poll;
 }
 
+bool rlc_am_nr_tx::do_status()
+{
+  return rx->get_do_status();
+}
+
 void rlc_am_nr_tx::reestablish()
 {
   stop();
@@ -395,12 +400,20 @@ bool rlc_am_nr_tx::sdu_queue_is_full()
 
 void rlc_am_nr_tx::empty_queue() {}
 
-bool rlc_am_nr_tx::do_status()
+void rlc_am_nr_tx::stop() {}
+/*
+ * Window helpers
+ */
+uint32_t rlc_am_nr_tx::tx_mod_base_nr(uint32_t sn) const
 {
-  return rx->get_do_status();
+  return (sn - st.tx_next_ack) % mod_nr;
 }
 
-void rlc_am_nr_tx::stop() {}
+bool rlc_am_nr_tx::inside_tx_window(uint32_t sn)
+{
+  // TX_Next_Ack <= SN < TX_Next_Ack + AM_Window_Size
+  return tx_mod_base_nr(sn) < RLC_AM_NR_WINDOW_SIZE;
+}
 
 /****************************************************************************
  * Rx subclass implementation
diff --git a/lib/test/rlc/rlc_am_nr_test.cc b/lib/test/rlc/rlc_am_nr_test.cc
index ce2e51788..c9ebc469b 100644
--- a/lib/test/rlc/rlc_am_nr_test.cc
+++ b/lib/test/rlc/rlc_am_nr_test.cc
@@ -82,6 +82,10 @@ int window_checker_test()
     TESTASSERT_EQ(true, rx->inside_rx_window(sn_inside_above));
     TESTASSERT_EQ(false, rx->inside_rx_window(sn_outside_below));
     TESTASSERT_EQ(false, rx->inside_rx_window(sn_outside_above));
+    TESTASSERT_EQ(true, tx->inside_tx_window(sn_inside_below));
+    TESTASSERT_EQ(true, tx->inside_tx_window(sn_inside_above));
+    TESTASSERT_EQ(false, tx->inside_tx_window(sn_outside_below));
+    TESTASSERT_EQ(false, tx->inside_tx_window(sn_outside_above));
   }
 
   rlc_am_nr_rx_state_t rx_st = {};
@@ -102,6 +106,10 @@ int window_checker_test()
     TESTASSERT_EQ(true, rx->inside_rx_window(sn_inside_above));
     TESTASSERT_EQ(false, rx->inside_rx_window(sn_outside_below));
     TESTASSERT_EQ(false, rx->inside_rx_window(sn_outside_above));
+    TESTASSERT_EQ(true, tx->inside_tx_window(sn_inside_below));
+    TESTASSERT_EQ(true, tx->inside_tx_window(sn_inside_above));
+    TESTASSERT_EQ(false, tx->inside_tx_window(sn_outside_below));
+    TESTASSERT_EQ(false, tx->inside_tx_window(sn_outside_above));
   }
   return SRSRAN_SUCCESS;
 }